Online Patching is new feature which is major change with R12 12.2 for DBA's , as downtime would be reduced for any patching activity from hours to few minutes.
Now it is possible to apply even upgrade patches in Online Patching mode minimizing downtime to very low, But please note upgrade to 12.2 is not possible via online patching from lower versions .
On the technology part of online patching, It is some what similar to Stage APPLTOP, But in online patching database objects also will maintain two copies to support this method. i.e. run file system and run edition of DB, patch file system and patch edition of DB.
In applications contains two set of file systems patch and run file system, run is where actually applications is running from and patch is used for patching the applications when it is running. in database we have edition based concept, where we contain patch edition and run edition.
Actually the base for the online patching concept came into picture with 11GR2 database version , Where there is concept called "Edition Based Redefinition", Online patching database part is based on it.
Online Patching in 12.2. is done using adop utility (No Longer adpatch), But this utility calls internally the required patching(adpatch) or other utilities.
and all the patches need to be applied using adop only, Other methods are not supported. But we can apply the patches in hot patch mode using adop, But in this method , The online patching concept will not come into picture , It is traditional way of applying patch directly on the run file system and run edition of the database when applications and DB is running.
Online Patching (adop) runs in different phases, The below are phases and syntax of adop.
prepare
apply
finalize
cutover
cleanup
prepare Phase
patch edition and run editions are synchronized in incremental synchronizations of files changed in the run file system.
patch edition is created in the database
Syntax: $ adop phase=prepare
apply phase
patches are applied to patch patch edition in the database and patch file system in the applications.
adpatch is called internally by adop to apply the patches.
production application is un effected by these changes, and multiple patches can be applied.
Syntax: $ adop phase=apply
To Apply specific patch in 12.2 using adop is :
$ adop phase=apply patches=17323764
finalize phase
Performs all the activities which can be done when applications is up & running.
example: compile invalids, generate objects, pre-compile DDL
Syntax: $ adop phase=finalize
This stage we can stay as long as we want, until once we have downtime to move the changed in the cutover stage ,
cutover phase
This is a stage where actual changes reflects and downtime is required for this stage.
Users are logged off during this stage.
patch file system is promoted to be the run file system
patch database edition is promoted to the run database edition.
users are actually brought back on online on the patched system.
Syntax: $ adop phase=cutover
cleanup phase
Cleanup happens once users online on the system
There are no cleanup on the file system , Only it happens on the database where it deletes the code objects from old editions of the database where patching happened.
Syntax: $ adop phase=cleanup
cutover phase
This is a stage where actual changes reflects and downtime is required for this stage.
Users are logged off during this stage.
patch file system is promoted to be the run file system
patch database edition is promoted to the run database edition.
users are actually brought back on online on the patched system.
Syntax: $ adop phase=cutover
cleanup phase
Cleanup happens once users online on the system
There are no cleanup on the file system , Only it happens on the database where it deletes the code objects from old editions of the database where patching happened.
Syntax: $ adop phase=cleanup
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